Paper Sheet Stacking Apparatus and Image Forming System

ABSTRACT

A paper sheet stacking apparatus, includes: a first tray that stacks a paper sheet; a sheet discharger that discharges a paper sheet supplied from the outside of the apparatus to the first tray; a second tray that receives the paper sheet stacked on the first tray and discharges the received paper sheet to the outside of the apparatus; and a hardware processor that controls operation states of the first tray and the second tray, wherein the first tray and the second tray have: a first operation state in which the first tray is positioned at a paper sheet stacking position; a second operation state in which the paper sheet stacked on the first tray is deliverable to the second tray; and a third operation state in which the first tray that has delivered the paper sheet to the second tray is returned to the paper sheet stacking position.

This application claims priority under 35 U.S.C. § 119 to Japanese patent Application No. 2018-195501, filed on Oct. 17, 2018, the entire disclosure of which is incorporated herein by reference.

BACKGROUND Technological Field

The present invention relates to a paper sheet stacking apparatus and an image forming system.

Description of the Related Art

A paper sheet stacking apparatus that stacks a large amount of paper sheets supplied from the outside of the paper sheet stacking apparatus is conventionally known. In this type of paper sheet stacking apparatus, there is known a configuration in which a tray configured to stack paper sheets and a carriage capable of transporting the paper sheets to the outside of the paper sheet stacking apparatus are included and delivery of the paper sheets to the carriage can be performed for each tray. According to this configuration, when the paper sheets are transported to the outside of the paper sheet stacking apparatus by the carriage, the paper sheets can be delivered together with the tray to the carriage, and therefore a large amount of stacked paper sheets can be easily handled.

For example, JP 2008-94581 A discloses a paper sheet stacking apparatus (sheet stacking apparatus) including a tray lifting and lowering member, a tray means, a driving means, a control means, and a carrier means. The tray means is attached to the tray lifting and lowering member in an attachable and detachable manner and configured to stack paper sheets (sheets) from a discharge port. The driving means is configured to lift and lower the tray lifting and lowering member below the discharge port. The control means is configured to control the driving means. The carrier means is configured to attach thereto the tray means separated from the tray elevating member and transport the tray means to the outside of the paper sheet stacking apparatus. In this case, the tray lifting and lowering member and the carrier means are configured to take over the tray means from each other and attach the tray means thereto at an attaching and detaching position to which the tray lifting and lowering member has lowered.

However, according to a technique disclosed in JP 2008-94581 A, the paper sheet is delivered to the carriage together with the tray. Therefore, there is a disadvantage that discharge of the paper sheet needs to be stopped from when the tray inside the paper sheet stacking apparatus is delivered to the carriage until the tray is returned to the inside of the paper sheet stacking apparatus, which causes downtime to occur.

SUMMARY

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a paper sheet stacking apparatus and an image forming system capable of suppressing the occurrence of downtime.

To achieve the abovementioned object, according to an aspect of the present invention, a paper sheet stacking apparatus reflecting one aspect of the present invention comprises: a first tray that stacks a paper sheet; a sheet discharger that discharges a paper sheet supplied from the outside of the paper sheet stacking apparatus to the first tray; a second tray that receives the paper sheet stacked on the first tray and discharges the received paper sheet to the outside of the paper sheet stacking apparatus; and a hardware processor that controls operation states of the first tray and the second tray, wherein the first tray and the second tray have: a first operation state in which the first tray is positioned at a paper sheet stacking position at which the paper sheet discharged from the sheet discharger is stacked and the second tray is positioned below the first tray; a second operation state in which an upper surface of the second tray is positioned above an upper surface of the first tray and the paper sheet stacked on the first tray is deliverable to the second tray; and a third operation state in which the first tray that has delivered the paper sheet to the second tray is returned to the paper sheet stacking position.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages and features provided by one or more embodiments of the invention will become more fully understood from the detailed description given hereinbelow and the appended drawings which are given by way of illustration only, and thus are not intended as a definition of the limits of the present invention:

FIG. 1 is a front view schematically showing a configuration of an image forming system according to a first embodiment;

FIG. 2 is a configuration view showing the main parts of a paper sheet stacking apparatus mainly including a first tray and a second tray;

FIG. 3 is a descriptive view showing a relationship between the second tray and the first tray;

FIG. 4 is a flowchart showing a flow of the operation of the image forming system;

FIGS. 5A to 5F are descriptive views for describing a flow of the operation of the paper sheet stacking apparatus;

FIG. 6 is a descriptive view showing a configuration of a paper sheet stacking apparatus according to a second embodiment;

FIGS. 7A to 7E are views for describing an outline of a flow of the operation of the paper sheet stacking apparatus according to the second embodiment;

FIG. 8 is a descriptive view showing a configuration of a paper sheet stacking apparatus according to a third embodiment;

FIGS. 9A to 9F are views for describing an outline of a flow of the operation of the paper sheet stacking apparatus according to the third embodiment;

FIG. 10 is a front view of the paper sheet stacking apparatus showing a modification of the first tray and the second tray; and

FIGS. 11A to 11C are views for describing an outline of a flow of the operation of the modification of the first tray and the second tray.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the disclosed embodiments.

First Embodiment

FIG. 1 is a front view schematically showing a configuration of an image forming system according to the present embodiment. The image forming system according to the present embodiment includes an image forming apparatus 1 and a paper sheet stacking apparatus 2.

The image forming apparatus 1 is an electrophotographic image forming apparatus such as a copying machine and is configured to form an image on a paper sheet P on the basis of image data. The image forming apparatus 1 includes a document reading device 5, a photoreceptor 11, a charging part 12, an image exposing part 13, a developing part 14, a transfer part 15A, a separator 15B, a cleaning device 16, a fixing device 18, and an image formation controller 19.

The document reading device 5 is disposed on the upper part of a housing of the image forming apparatus 1 and includes an automatic document feeder configured to automatically move a document when an image is read. The document reading device 5 is configured to read the image formed on the document and output a predetermined image signal. The output image signal is created as image data by being subjected to an analog-to-digital conversion.

An image reading controller (not shown) included in the document reading device 5 is configured to subject the image data to processing such as shading correction, dither processing, compression and output data obtained by the processing, as final image data, to the image formation controller 19. Note that the image formation controller 19 not only obtains the image data from the document reading device 5 but also may obtain image data from a personal computer connected to the image forming apparatus 1 or another image forming apparatus 1.

The surface of the photoreceptor 11 is uniformly charged by the charging part 12. The image exposing part 13 is configured to scan and expose the surface of the photoreceptor 11 with a laser beam on the basis of output information output from the image formation controller 19 on the basis of the image data. Thus, a latent image is formed on the surface of the photoreceptor 11. The developing part 14 is configured to develop the latent image with toner to form an image (toner image) on the surface of the photoreceptor 11.

The paper sheet P accommodated in a paper sheet tray 17A is fed to the transfer part 15A. The transfer part 15A is configured to transfer the image on the surface of the photoreceptor 11 to the paper sheet P. The separator 15B is configured to separate the paper sheet P to which the image is transferred from the photoreceptor 11. The cleaning device 16 is configured to remove the toner remaining on the surface of the photoreceptor 11 after the image is transferred to the paper sheet P. An intermediate conveyance part 17B is configured to convey the separated paper sheet P to the fixing device 18.

The fixing device 18 is configured to subject the paper sheet P to fixing processing to fix the image by heating and pressing. A paper sheet discharge roller 17C is configured to discharge the paper sheet P subjected to the fixing processing to the outside of the image forming apparatus 1.

Meanwhile, when an image is formed on both sides of the paper sheet P, an conveyance direction of the paper sheet P subjected to the fixing processing by the fixing device 18 is switched from a side of the paper sheet discharge roller 17C to a lower side (side of a reverse conveyance part 17E) by a conveyance path switching plate 17D. The reverse conveyance part 17E is configured to reverse the front and back of the paper sheet P by switching back the paper sheet P and then convey the paper sheet P to the transfer part 15A.

The image formation controller 19 is configured to control the image forming apparatus 1. As the image formation controller 19, a microcomputer mainly including a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input/output (I/O) interface can be used. The CPU is configured to execute various programs (processors). The ROM is configured to store various programs executed by the CPU in the form of program codes readable by the CPU. Furthermore, the ROM is configured to store data necessary for execution of the programs. The RAM is a memory configured to serve as a working storage area. The programs and data stored in the ROM are expanded on the RAM when the programs and data are read by the CPU. Then, the CPU is configured to perform various processing on the basis of the programs and data expanded on the RAM.

The paper sheet stacking apparatus 2 is an apparatus configured to stack and accommodate the paper sheet P when the paper sheet P supplied from the image forming apparatus 1 is taken into the inside of the paper sheet stacking apparatus 2. The paper sheet stacking apparatus 2 is disposed on a downstream side of the image forming apparatus 1 in a paper sheet conveyance direction so that the paper sheet stacking apparatus 2 is adjacent to the image forming apparatus 1. The paper sheet stacking apparatus 2 mainly includes a paper sheet discharger 20, a first tray 21, a lifting and lowering device 24, a second tray 25, a front-rear driving device 28, and a stacking controller 31. Here, FIG. 2 is a configuration view showing the main parts of the paper sheet stacking apparatus 2 mainly including the first tray 21 and the second tray 25.

When receiving the paper sheet P supplied from the image forming apparatus 1, the paper sheet discharger 20 takes the paper sheet P into the inside of the paper sheet stacking apparatus 2 (inside of a housing 2 a) and discharges the paper sheet P into the first tray 21. A position of the paper sheet discharger 20 is set to correspond to a position of the paper sheet discharge roller 17C of the image forming apparatus 1.

The first tray 21 is a tray on which the paper sheet P discharged from the paper sheet discharger 20 is stacked. The first tray 21 is movable along an up-and-down direction. The first tray 21 includes a plurality of first support members 22 formed in a comb shape. The plurality of first support members 22 is arranged horizontally at a predetermined pitch along the paper sheet conveyance direction. Each first support member 22 extends from a base member 23 positioned on a rear side (rear side of the paper sheet stacking apparatus 2) to a front side (front side of the paper sheet stacking apparatus 2).

The lifting and lowering device 24 is a device configured to lift and lower (move) the first tray 21 along the up-and-down direction. The lifting and lowering device 24 mainly includes a drive motor, a drive pulley, a driven pulley, and a timing belt. The drive pulley is configured to rotate by receiving power from the drive motor. The timing belt is stretched between the drive pulley and the driven pulley and connects the first tray 21. The lifting and lowering device 24 is controlled by the stacking controller 31.

The lifting and lowering device 24 is configured to set the first tray 21 to a home position. The home position corresponds to a position of the first tray 21 when the stacking of the paper sheet P is started. When the paper sheet P is discharged from the paper sheet discharger 20, the lifting and lowering device 24 lowers (moves) the first tray 21 so that the uppermost paper sheet P stacked on the first tray 21 maintains a predetermined height. The lowering of the first tray 21 in association with the stacking of the paper sheet P is performed until the number of the paper sheets P stacked on the first tray 21 reaches the upper limit number of paper sheets or the set number of paper sheets. The upper limit number of paper sheets is set by setting the maximum number of the paper sheets P that can be stacked on the first tray 21. The upper limit number of paper sheets is set, for example, by mechanical restrictions caused by the structure of the paper sheet stacking apparatus 2. Meanwhile, the set number of paper sheets is, for example, the number of the paper sheets set by a user within the maximum number of the paper sheets P to be stacked on the first tray 21 and any number of the paper sheets is set in the range of one or more paper sheets and less than the upper limit number of paper sheets. Positions from the home position to a position at which the first tray 21 reaches when the paper sheets P, the number of which corresponds to the upper limit number of paper sheets are stacked correspond to a paper sheet stacking position of the first tray 21.

Meanwhile, when the number of the paper sheets P stacked on the first tray 21 has reached the upper limit number of paper sheets or the set number of paper sheets, the lifting and lowering device 24 lowers the first tray 21 to a paper sheet delivery position at which the paper sheet P is delivered to the second tray 25. Furthermore, when the delivery of the paper sheet P from the first tray 21 to the second tray 25 is completed, the lifting and lowering device 24 lifts (moves) the first tray 21 from the paper sheet delivery position to the home position.

The second tray 25 is disposed below the first tray 21. The second tray 25 is a tray for receiving the paper sheet P stacked on the first tray 21 from the first tray 21. The second tray 25 includes a plurality of second support members 26 formed in a comb shape. The plurality of second support members 26 is arranged horizontally at a predetermined pitch along the paper sheet conveyance direction. Each second support member 26 stands on a base member 27 positioned below the second support member 26.

FIG. 3 is a descriptive view showing a relationship between the second tray 25 and the first tray 21. The plurality of second support members 26 is provided at positions corresponding to a plurality of clearances formed in the first tray 21, that is, spaces existing between the first support members 22 adjacent to each other. Therefore, even in a case where the first tray 21 moves downward and the first tray 21 and the second tray 25 exist on the same horizontal plane, the first tray 21 and the second tray 25 do not interfere with each other. That is, the first tray 21 and the second tray 25 can pass each other in the up-and-down direction. With this configuration, an upper surface 21 a of the first tray 21 is lowered below an upper surface 25 a of the second tray 25, whereby the paper sheet P stacked on the first tray 21 can be delivered to the second tray 25. The paper sheet delivery position described above is determined in advance according to a height of the second tray 25, as a position at which the upper surface 21 a of the first tray 21 exists below the upper surface 25 a of the second tray 25.

The front-rear driving device 28 includes a pedestal part 29 and a driving part 30. On the pedestal part 29, the second tray 25 is mounted in an attachable and detachable manner. The driving part 30 is configured to move the pedestal part 29 along a front-rear direction and discharge the second tray 25 to the outside of the paper sheet stacking apparatus 2. The driving part 30 mainly includes a driving motor, a driving pulley, a driven pulley, and a timing belt. The driving pulley is configured to rotate by receiving power from the driving motor. The timing belt is stretched between the driving pulley and the driven pulley and connects the pedestal part 29. The front-rear driving device 28 is controlled by the stacking controller 31.

The front-rear driving device 28 is configured to set the second tray 25 to the home position. The home position exists below the first tray 21 inside the paper sheet stacking apparatus 2 and is a position at which the paper sheet P can be delivered from the first tray 21 when the first tray 21 has lowered. When the paper sheet P is delivered from the first tray 21, the front-rear driving device 28 moves the second tray 25 to the front side and discharges the second tray 25 to the outside of the paper sheet stacking apparatus 2. Thus, when the second tray 25 is removed from the pedestal part 29, the second tray 25 is attached to a carriage 40 configured to convey the paper sheet P. As a result, the paper sheet P can be conveyed together with the second tray 25 through the carriage 40.

Meanwhile, when the paper sheet P is removed from the second tray 25 mounted on the carriage 40, the second tray 25 is removed from the carriage 40 and attached to the pedestal part 29. When the second tray 25 is attached to the pedestal part 29, the front-rear driving device 28 moves the second tray 25 to the rear side and returns the second tray 25 to the home position. Note that the housing 2 a of the paper sheet stacking apparatus 2 is provided with a shutter (not shown). The shutter is opened and closed according to the entry and exit of the second tray 25.

The stacking controller 31 is configured to control the paper sheet stacking apparatus 2. As the stacking controller 31, a microcomputer mainly including a CPU, a ROM, a RAM, and an I/O interface can be used. The CPU is configured to execute various programs (processors). The ROM is configured to store various programs executed by the CPU in the form of program codes readable by the CPU. Furthermore, the ROM is configured to store data necessary for execution of the programs. The RAM is a memory configured to serve as a working storage area. The programs and data stored in the ROM are expanded on the RAM when the programs and data are read by the CPU. Then, the CPU is configured to perform various processing on the basis of the programs and data expanded on the RAM.

Hereinafter, the operation of the image forming system according to the present embodiment will be described. Here, FIG. 4 is a flowchart showing a flow of the operation of the image forming system. Furthermore, FIGS. 5A to 5F are views for describing a flow of the operation of the paper sheet stacking apparatus 2. Processing shown in the flowchart is executed by the image formation controller 19 and the stacking controller 31 using a print start instruction of the user as a trigger.

First, in step S10, the image formation controller 19 controls each part of the image forming apparatus 1 to execute image forming operation. By this image forming operation, a series of processing such as sheet feeding of the paper sheet P, image formation on the fed paper sheet P, and discharge of the paper sheet P on which the image is formed to the paper sheet stacking apparatus 2 is performed. Similarly, the stacking controller 31 controls the paper sheet discharger 20, receives the paper sheet P supplied from the image forming apparatus 1 at the paper sheet discharger 20, and discharges the paper sheet P to the first tray 21 (FIG. 5A).

In step S11, the stacking controller 31 determines whether the number of the paper sheets P stacked on the first tray 21 has reached the upper limit number of paper sheets or the set number of paper sheets. In a case where the number of the paper sheets P stacked on the first tray 21 has reached the upper limit number of paper sheets or the set number of paper sheets, a positive determination is made in step S11, and the processing proceeds to step S12. Meanwhile, when the number of the paper sheets P stacked on the first tray 21 has not reached the upper limit number of paper sheets or the set number of paper sheets, a negative determination is made in step S11, and the processing returns to step S10.

In step S12, the image formation controller 19 controls each part of the image forming apparatus 1 to stop the image forming operation. Similarly, the stacking controller 31 controls the paper sheet discharger 20 to stop sheet discharge of the paper sheet P to the first tray 21.

In step S13, the stacking controller 31 controls the lifting and lowering device 24 to cause the first tray 21 to perform lowering operation (FIG. 5B). The lowering operation of the first tray 21 is performed until the first tray 21 reaches the paper sheet delivery position. The paper sheet delivery position is set according to the height of the second tray 25 mounted on the pedestal part 29. When the first tray 21 reaches the paper sheet delivery position, since the upper surface 25 a of the second tray 25 reaches above the upper surface 21 a of the first tray 21, the paper sheet P stacked on the first tray 21 is delivered from the first tray 21 to the second tray 25 (FIG. 5C).

In step S14, the stacking controller 31 controls the front-rear driving device 28 to cause the pedestal part 29 to perform forward operation (FIG. 5D). This forward operation is performed until the pedestal part 29 and the second tray 25 mounted on the pedestal part 29 are discharged to the outside of the paper sheet stacking apparatus 2.

In step S15, the stacking controller 31 controls the lifting and lowering device 24 to cause the lift the first tray 21 to perform upward operation (FIG. 5E). The lifting operation of the first tray 21 is performed until the first tray 21 reaches the home position.

The second tray 25 discharged to the outside of the paper sheet stacking apparatus 2 is removed from the pedestal part 29 with the paper sheet P stacked and is attached to the carriage 40 provided outside the paper sheet stacking apparatus 2 (FIG. 5F). The second tray 25 and the paper sheet P stacked on the second tray 25 can be conveyed through the carriage 40.

In step S16, the image formation controller 19 controls each part of the image forming apparatus 1 to restart the image forming operation. Similarly, the stacking controller 31 controls the paper sheet discharger 20 to restart the discharge of the paper sheet P to the first tray 21. The restart of the image forming operation and the restart of sheet discharge to the first tray 21 are executed so that the paper sheet P is discharged to the first tray 21 at timing when the first tray 21 has reached the home position or at timing slightly later than when the first tray 21 has reached the home position.

In step S17, the image formation controller 19 determines whether the job has ended. In a case where the job has ended, a positive determination is made in step S17, and this routine ends. Meanwhile, in a case where the job has not ended, a negative determination is made in step S17, and the processing returns to step S10.

When the paper sheet P stacked on the second tray 25 is removed and the second tray 25 is emptied, the second tray 25 is removed from the carriage 40 and attached to the pedestal part 29. When the second tray 25 is attached, the stacking controller 31 controls the front-rear driving device 28 to cause the pedestal part 29 to perform backward operation. This backward operation is performed until the pedestal part 29 and the second tray 25 mounted on the pedestal part 29 reach the home position. Thus, the second tray 25 is returned to the inside of the paper sheet stacking apparatus 2.

Note that the second tray 25 is preferably returned to the pedestal part 29 before the number of the paper sheets P stacked on the first tray 21 reaches the upper limit number of paper sheets or the set number of paper sheets. Furthermore, since there is a possibility that the pedestal part 29 becomes an obstacle if the pedestal part 29 stays discharged to the outside of the paper sheet stacking apparatus 2, the pedestal part 29 may be returned to the inside of the paper sheet stacking apparatus 2 until the second tray 25 is removed from the pedestal part 29 and then may be attached to the pedestal part 29 again.

As described above, in the present embodiment, the first tray 21 and the second tray 25 have at least three operation states as operation states thereof. Specifically, a first operation state is an operation state in which the first tray 21 is at the paper sheet stacking position at which the paper sheet P discharged from the paper sheet discharger 20 is stacked, and the second tray 25 is positioned below the first tray 21. A second operation state is an operation state in which the upper surface 25 a of the second tray 25 is positioned above the upper surface 21 a of the first tray 21, and the paper sheet P stacked on the first tray 21 can be delivered to the second tray 25. Furthermore, a third operation state is an operation state in which the first tray 21 that has delivered the paper sheet P to the second tray 25 is returned to the paper sheet stacking position.

According to this configuration, since the paper sheet P can be delivered to the second tray 25, the paper sheet P can be taken out of the paper sheet stacking apparatus 2 via the second tray 25 while the first tray 21 is left in the paper sheet stacking apparatus 2. Furthermore, the first tray 21 that has delivered the paper sheet P to the second tray 25 can be returned to the paper sheet stacking position (home position). Therefore, the stacking of the paper sheet P on the first tray 21 can be restarted promptly. As a result, the occurrence of downtime can be suppressed.

Furthermore, each of the first tray 21 and the second tray 25 includes clearances for passing the other tray so that the first tray 21 and the second tray 25 do not interfere with each other on the same plane. Specifically, the first tray 21 and the second tray 25 are each set in a comb shape.

According to this configuration, since the first tray 21 and the second tray 25 do not interfere with each other on the same plane, the upper surface 21 a of the first tray 21 can be reached below the upper surface 25 a of the second tray 25. Thus, the paper sheet P can be easily delivered from the first tray 21 to the second tray 25.

Furthermore, in the paper sheet stacking apparatus 2 according to the present embodiment, the first tray 21 reaches the paper sheet delivery position according to the height of the second tray 25, whereby the first operation state changes to the second operation state.

According to this configuration, the paper sheet P can be easily delivered from the first tray 21 to the second tray 25 by moving the first tray 21.

Furthermore, in the present embodiment, in the first operation state, the second tray 25 is positioned below the first tray 21 and the first tray lowers, whereby the first operation state changes to the second operation state.

According to this configuration, the paper sheet P can be easily delivered from the first tray 21 to the second tray 25 by moving the first tray 21 in the up-and-down direction. Furthermore, since the first tray 21 has a function of lifting and lowering in the up-and-down direction when the paper sheet P is stacked, the paper sheet P can be delivered from the first tray 21 to the second tray 25, using the existing configuration.

Furthermore, in the present embodiment, the paper sheet stacking apparatus 2 further includes the pedestal part 29 configured to move between the inside of the paper sheet stacking apparatus 2 and the outside of the paper sheet stacking apparatus 2. In this case, the second tray 25 is mounted on the pedestal part 29. According to this configuration, the second tray 25 can be moved between the inside of the paper sheet stacking apparatus 2 and the outside of the paper sheet stacking apparatus 2 by moving the pedestal part 29.

Furthermore, in the present embodiment, the second tray 25 is mounted on the pedestal part 29 in an attachable and detachable manner. According to this configuration, since the second tray 25 can be attached and detached, the paper sheet P can be handled together with the second tray 25.

Furthermore, in the present embodiment, the paper sheet stacking apparatus 2 further includes the carriage 40 on which the second tray 25 discharged to the outside of the paper sheet stacking apparatus 2 is mounted and that is configured to convey the second tray 25.

According to this configuration, since the second tray 25 can be transported by the carriage 40, a large amount of the paper sheets P can be easily conveyed.

Second Embodiment

Hereinafter, an image forming system according to a second embodiment will be described. The image forming system according to the second embodiment differs from that according to the first embodiment in the configuration of the paper sheet stacking apparatus 2. Descriptions of contents overlapping the first embodiment will be omitted, and hereinafter, differences will be mainly described.

FIG. 6 is a descriptive view showing a configuration of a paper sheet stacking apparatus 2 according to the second embodiment. The paper sheet stacking apparatus 2 mainly includes a paper sheet discharger 20 (not shown in FIG. 6), a first tray 21, a lifting and lowering device 24, a second tray 25, a carriage 40, and a stacking controller 31. Configurations of the paper sheet discharger 20, the first tray 21, the lifting and lowering device 24, and the stacking controller 31 are similar to those in the first embodiment.

In the present embodiment, the second tray 25 is mounted on the carriage 40 accommodated inside the paper sheet stacking apparatus 2. The carriage 40 is configured to convey the second tray 25 and can be moved from the inside of the paper sheet stacking apparatus 2 to the outside of the paper sheet stacking apparatus 2.

Hereinafter, the operation of the paper sheet stacking apparatus 2 according to the present embodiment will be described. FIGS. 7A to 7E are views for describing an outline of a flow of the operation of the paper sheet stacking apparatus 2 according to the second embodiment.

First, discharge of a paper sheet P discharged from an image forming apparatus 1 to the first tray 21 is started (FIG. 7A). When the number of the paper sheets P stacked on the first tray 21 reaches the upper limit number of paper sheets or the set number of paper sheets, the stacking controller 31 controls the lifting and lowering device 24 to cause the lower the first tray 21 to perform lowering operation (FIG. 7B). The lowering operation of the first tray 21 is performed until the first tray 21 reaches the paper sheet delivery position. The paper sheet delivery position is set according to a height of the second tray 25 mounted on the carriage 40. When the first tray 21 reaches the paper sheet delivery position, since an upper surface 25 a of the second tray 25 reaches above an upper surface 21 a of the first tray 21, the paper sheet P stacked on the first tray 21 is delivered from the first tray 21 to the second tray 25 (FIG. 7C).

The carriage 40 from which the paper sheet P has been delivered to the second tray 25 is carried out of the paper sheet stacking apparatus 2 by a user (FIG. 7D). When the stacking controller 31 determines that the carriage 40 has been carried out of the paper sheet stacking apparatus 2, using a detection result of a sensor (not shown), the stacking controller 31 controls the lifting and lowering device 24 to cause the first tray 21 to perform upward operation (see FIG. 7E). The lifting operation of the first tray 21 is performed until the first tray 21 reaches the home position.

The second tray 25 carried out together with the carriage 40 can be conveyed to a target location through the carriage 40. Then, the first tray 21 returns to the home position, whereby image forming operation and the discharge of the paper sheet P to the first tray 21 are started.

As described above, according to the present embodiment, the second tray 25 is mounted on the carriage 40, and the carriage 40 is accommodatable inside the paper sheet stacking apparatus 2.

According to this configuration, the second tray 25 and the paper sheet P can be moved between the outside and the inside of the paper sheet stacking apparatus 2, using the carriage 40. Furthermore, since the carriage 40 is accommodated inside the paper sheet stacking apparatus 2, there is no need to transfer the second tray 25 to the carriage 40. Thus, the paper sheet P delivered from the first tray 21 can be easily conveyed.

Third Embodiment

Hereinafter, an image forming system according to a third embodiment will be described. The image forming system according to the third embodiment differs from that the first embodiment in the configuration of the paper sheet stacking apparatus 2. Hereinafter, descriptions of contents overlapping with the first embodiment will be omitted, and hereinafter, differences will be mainly described.

FIG. 8 is a descriptive view showing a configuration of a paper sheet stacking apparatus 2 according to the third embodiment. The paper sheet stacking apparatus 2 mainly includes a paper sheet discharger 20 (not shown in FIG. 8), a first tray 21, a lifting and lowering device 24, a plurality of second trays 25, a front-rear driving device 28, and a stacking controller 31. Configurations of the paper sheet discharger 20, the first tray 21, the lifting and lowering device 24, the front-rear driving device 28, and the stacking controller 31 are similar to those in the first embodiment.

In the present embodiment, the plurality of second trays 25 is mounted on a pedestal part 29 while being stacked in an up-and-down direction. A configuration of each second tray 25 is similar to that of the first embodiment.

Hereinafter, the operation of the paper sheet stacking apparatus 2 according to the present embodiment will be described. FIGS. 9A to 9F are views for describing an outline of a flow of the operation of the paper sheet stacking apparatus 2 according to the third embodiment.

First, when a paper sheet P discharged from an image forming apparatus 1 is discharged to the first tray 21 and the number of the paper sheets P stacked on the first tray 21 reaches the upper limit number of paper sheets or the set number of paper sheets, the stacking controller 31 controls the lifting and lowering device 24 to cause the first tray 21 to perform lowering operation (FIG. 9A). The lowering operation of the first tray 21 is performed until the first tray 21 reaches the paper sheet delivery position. The paper sheet delivery position is set according to a height of the uppermost second tray 25 among the plurality of second trays 25 mounted on the pedestal part 29. More specifically, the paper sheet delivery position is set to be in a relationship such that an upper surface 25 a of the uppermost second tray 25 is positioned above an upper surface 21 a of the first tray 21 when the first tray 21 reaches the paper sheet delivery position. When the first tray 21 reaches the paper sheet delivery position, since the upper surface 25 a of the uppermost second tray 25 reaches above the upper surface 21 a of the first tray 21, the paper sheet P stacked on the first tray 21 is delivered from the first tray 21 to the uppermost second tray 25 (FIG. 9B).

When delivery of the paper sheet P to the second tray 25 is performed, the pedestal part 29 is caused to perform forward operation, whereby the second tray 25 is discharged to the outside of the paper sheet stacking apparatus 2. Thus, the uppermost second tray 25 is removed from the pedestal part 29 and attached to a carriage 40 provided outside the paper sheet stacking apparatus 2. When the uppermost second tray 25 is attached to the carriage 40, the pedestal part 29 is returned to a home position. Thus, the remaining second tray 25 return to the inside of the paper sheet stacking apparatus 2 (FIG. 9C).

When the remaining second trays 25 return to the inside of the paper sheet stacking apparatus 2, the stacking controller 31 controls the lifting and lowering device 24 to cause the first tray 21 to perform upward operation (FIG. 9D). The lifting operation of the first tray 21 is performed until the first tray 21 reaches the home position. The first tray 21 returns to the home position, whereby the image forming operation and the discharge of the paper sheet P to the first tray 21 are started. Then, the above operation is repeated for the new uppermost second tray 25 (FIGS. 9E and 9F).

As described above, in the present embodiment, the plurality of second trays 25 is stacked in the up-and-down direction. In this case, the paper sheet delivery position is switched according to a height of the second tray 25 positioned at the uppermost position.

According to this configuration, since the plurality of second trays 25 is provided, even if one second tray 25 is discharged to the outside of the paper sheet stacking apparatus 2, the paper sheet P can be delivered to the second tray 25 remaining on the pedestal part 29 without waiting until the second tray 25 returns. Thus, the occurrence of downtime can be suppressed.

Note that in each embodiment described above, each of the first tray 21 and the second tray 25 includes clearances for passing the tray on the other side so that the first tray 21 and the second tray 25 do not interfere with each other on the same plane. However, a method of delivering the paper sheet P from the first tray 21 to the second tray 25 is not limited to this. Here, FIG. 10 is a front view of the paper sheet stacking apparatus 2 showing a modification of the first tray 21 and the second tray 25.

Specifically, a second tray 25 is disposed on a side of a first tray so that the second tray 25 is arranged side by side with the first tray 21. According to this modification, the first tray 21 and the second tray 25 can suppress interference with each other on the same plane without including clearances for passing the tray on the other side.

In this modification, when the number of the paper sheets P stacked on the first tray 21 reaches the set number of paper sheets or the upper limit number of paper sheets, a stacking controller 31 controls a lifting and lowering device 24 to cause the first tray 21 to perform lowering operation (see FIG. 11A). The lowering operation of the first tray 21 is performed until the first tray 21 reaches the paper sheet delivery position. The paper sheet delivery position is set according to a height of the second tray 25 (FIG. 11B). More specifically, the paper sheet delivery position is set to be in a relationship such that an upper surface 25 a of the second tray 25 that is arranged side by side with the first tray 21 when the first tray 21 reaches the paper sheet delivery position is positioned above the upper surface 21 a of the first tray 21. The delivery of the paper sheet P from the first tray 21 to the second tray 25 can be performed using any method. For example, a belt conveyor is used. When the delivery of the paper sheet P is completed, the first tray 21 returns to a home position (FIG. 11C). Thus, the image forming operation and the discharge of the paper sheet P to the first tray 21 can be started.

Although the image forming system and the paper sheet stacking apparatus according to the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the invention.

For example, in the present embodiments, the image forming system includes the image forming apparatus configured to serve an image forming function and the paper sheet stacking apparatus configured to stack the paper sheet. However, a sheet processing device itself that constitutes the image forming system also functions as an aspect of the present invention. Furthermore, in addition to a configuration in which the image forming system includes the image forming apparatus and the paper sheet stacking apparatus as independent apparatuses, there may be a configuration in which an image forming system includes a paper sheet stacking apparatus as one function of an image forming apparatus.

Furthermore, in the present embodiments, the paper sheet stacking apparatus includes the dedicated controller (stacking controller), and the stacking controller executes control of the paper sheet stacking apparatus. However, the image formation controller configured to control the image forming apparatus may control the paper sheet stacking apparatus. In this case, the stacking controller may be omitted.

Furthermore, in the present embodiments, the paper sheet P widely includes not only a recording medium manufactured using pulp as a main raw material but also a recording medium capable of forming an image by the image forming apparatus.

Furthermore, in the present embodiments, the first tray is moved when the paper sheet is delivered. However, the second tray may be moved and reached to the paper sheet delivery position according to the height of the first tray, that is, a position at which the upper surface of the second tray is above the upper surface of the first tray, whereby the first operation state is changed to the second operation state. Furthermore, both the first tray and the second tray may be moved to change from the first operation state to the second operation state.

Although embodiments of the present invention have been described and illustrated in detail, the disclosed embodiments are made for purposes of illustration and example only and not limitation. The scope of the present invention should be interpreted by terms of the appended claims. 

What is claimed is:
 1. A paper sheet stacking apparatus, comprising: a first tray that stacks a paper sheet; a sheet discharger that discharges a paper sheet supplied from the outside of the paper sheet stacking apparatus to the first tray; a second tray that receives the paper sheet stacked on the first tray and discharges the received paper sheet to the outside of the paper sheet stacking apparatus; and a hardware processor that controls operation states of the first tray and the second tray, wherein the first tray and the second tray have: a first operation state in which the first tray is positioned at a paper sheet stacking position at which the paper sheet discharged from the sheet discharger is stacked and the second tray is positioned below the first tray; a second operation state in which an upper surface of the second tray is positioned above an upper surface of the first tray and the paper sheet stacked on the first tray is deliverable to the second tray; and a third operation state in which the first tray that has delivered the paper sheet to the second tray is returned to the paper sheet stacking position.
 2. The paper sheet stacking apparatus according to claim 1, wherein each of the first tray and the second tray includes a clearance for passing the other tray so that the first tray and the second tray do not interfere with each other on the same plane.
 3. The paper sheet stacking apparatus according to claim 1, wherein the first tray reaches a paper sheet delivery position according to a height of the second tray, whereby the first operation state changes to the second operation state.
 4. The paper sheet stacking apparatus according to claim 3, wherein in the first operation state, the second tray is positioned below the first tray, and the first tray lowers, whereby the first operation state changes to the second operation state.
 5. The paper sheet stacking apparatus according to claim 3, wherein a plurality of the second trays is stacked in an up-and-down direction, and the paper sheet delivery position is switched according to a height of the second tray positioned at an uppermost position.
 6. The paper sheet stacking apparatus according to claim 1, further comprising a pedestal part that moves between the inside of the paper sheet stacking apparatus and the outside of the paper sheet stacking apparatus, wherein the second tray is mounted on the pedestal part.
 7. The paper sheet stacking apparatus according to claim 6, wherein the second tray is mounted on the pedestal part in an attachable and detachable manner.
 8. The paper sheet stacking apparatus according to claim 1, further comprising a carriage on which the second tray is mounted and that conveys the second tray, wherein the carriage is accommodatable inside the paper sheet stacking apparatus.
 9. The paper sheet stacking apparatus according to claim 1, further comprising a carriage on which the second tray discharged to the outside of the paper sheet stacking apparatus is mounted and that conveys the second tray.
 10. The paper sheet stacking apparatus according to claim 1, wherein the second tray reaches a paper sheet delivery position according to the height of the first tray, whereby the first operation state changes to the second operation state.
 11. The paper sheet stacking apparatus according to claim 1, wherein each of the first tray and the second tray reaches a predetermined paper sheet delivery position, whereby the first operation state changes to the second operation state.
 12. An image forming system, comprising: an image forming apparatus that discharges a paper sheet on which an image is formed; and the paper sheet stacking apparatus according to claim 1 in which the paper sheet discharged from the image forming apparatus is stacked. 